Containers, in particular glass containers, for holding foodstuffs must be checked within the scope of the production process for any possible incline in their neck. If a neck comprises an incline which is outside a predetermined tolerance range, the container is rejected. Since bottling plants now operate at extremely high processing speeds and therefore the machines which close the containers operate very rapidly, the precision requirements of a neck are correspondingly high.
It is known from German Patent Publication DT 2145679 to check the neck of a container for a possible incline by placing a small cap in a sealing manner on to the periphery of the neck and drawing air from the hollow space formed by the container and the small cap in order to produce negative pressure. If the incline of the neck is too severe, the small cap will no longer lie in a sealing manner on the periphery of the neck, so that the negative pressure is not generated as desired. The small cap can be rigidly attached to a guide rod which is provided for placing on to the neck or, in its angle of inclination relative to the horizontal plane, the small cap can be attached in a flexible manner to the guide rod, whereby it is possible to adjust the tolerance range accordingly in relation to an incline in the neck. Alternatively, instead of generating negative pressure it is also possible to generate excess pressure as a checking criterion. However, these methods permit only a relatively low throughput of containers, as a certain amount of time is required to set the negative pressure or the excess pressure. Furthermore, in the case of these methods, it proves to be disadvantageous that the checking procedure only provides a pass or fail signal as the result. This method does not allow a more precise measurement of the severity of an incline to be taken.
Furthermore, the German utility model G 86 00 118 describes a device for checking the neck of containers which move along a path. The device comprises a checking head which can be lowered to a working position over the neck. When in the working position, the checking head rotates about the neck and in so doing emits light horizontally over an edge of the neck. The light is deflected upwards by means of a first deflecting element inserted partially into the neck and the light is projected on to photo-receivers by means of an optical system. Irregularities in the neck can be established by evaluating the output signals of the photo-receivers. This device is costly. In particular, in the case of this device it is provided that the containers are stopped in order to carry out the checking procedure. Checking the containers in the moving state would make the checking process, in particular the procedure of centering the checking head, a great deal more difficult.
German patent publication DE 38 34 986 A1 discloses a device for the continuous detection of the filling volume of liquids in containers, in particular horizontally installed cylindrical containers at gasoline stations. The device is designed in such a manner that it also detects the incline of the container in terms of measuring technology and takes this into consideration in relation to the liquid volume actually present. For this purpose, the device comprises a float system having floating bodies which are pivotable in relation to a guide tube which protrudes from above into the liquid, in order to adapt to the angular position of the guide tube with respect to the surface of the liquid. The angle between the surface of the liquid with respect to a reference surface of the container is detected electrically using a commercially available incline sensor (inclinometer). The known device does not serve to check the container for a possible inherent incline of its neck outside a tolerance range but on the contrary is used for the purpose of establishing a static or dynamic incline in the entire container in order to determine the liquid volume contained. For this purpose, the container must be filled with a liquid.